The present invention generally relates to a microcomputer control apparatus and an associated method for achieving a required control function by processing a program by way of a single chip microcomputer. More specifically, the present invention is directed to a microcomputer control apparatus and an associated method suitable for use in an engine control, of an automobile.
As is well known, programs are necessarily required for apparatuses which use computers.
Often, a central processing unit (CPU) employing therein a masked ROM (read-only memory), into which a program has been written during a manufacturing step, is used as a single chip microcomputer in a conventional control apparatus. However, this method may result in problems, since in a so-called "multi-sort/small quantity production" system, a considerable development cost is required, a lengthy development time is needed for modifying the program, thereby lowering the yield, and furthermore modifications of the program are not achieved with flexibility. Accordingly, in for example, engine control apparatuses, it is common to employ a CPU with an EPROM in which a program is readily rewritable. In this case, a choice may be made between one control apparatus with a multi-chip type microcomputer in which a PROM and a CPU are separately employed and an other control apparatus with a single chip type microcomputer in which a PROM is built in a CPU.
When program data is written into a single chip type microcomputer, before this computer is mounted or packaged on a circuit board, a predetermined exclusively-used jig is employed so as to permit electrical access to the PROM.
These types of apparatus are known in the art from, for instance,
JP-A-56-7295, PA1 JP-A-61-264594, and PA1 JP-A-63-188894.